Is popular culture like a river, flowing relentlessly forward so that no one ever steps in the same waters twice? Or is it like a coral reef — or, less organically, a landfill — formed out of the continuous accretion of new matter? If two wildly dissimilar objects have the same name, does it make any sense to compare them? If so, how? Please forgive the philosophical tenor of these questions: I’ve just seen “21 Jump Street,” and it has left me in a ruminative mood.

Not that the movie, directed by Phil Lord and Christopher Miller and based on the semi-beloved, dimly recalled Fox cop show that made Johnny Depp a star in the late 1980s, aims to be thought-provoking. It wants to be fun and, to a perhaps surprising extent, it is. Largely forsaking the sweet multiculturalism of the original for white-dude bromance, and completely abandoning earnest teenagers-in-crisis melodrama in favor of crude, aggressive comedy, this “21 Jump Street” is an example of how formula-driven entertainment can succeed.

It is full of the usual boy-comedy stuff: homophobic humor so blatant that it must be making fun of homophobia (right?); easy, knowing sendups of movie and television clichés; appearances by actors from your favorite sitcoms (assuming you like “The Office,” “Parks and Recreation” and “New Girl”); exploding cars; a joke about “Glee.” And though no conceptual ground is broken that wasn’t already trampled and scorched in the Harold and Kumar movies (to cite only the three most sophisticated examples), the whole mess is silly, spirited and, yes, smart enough to work.

Two high school classmates — an alpha dog named Jenko (Channing Tatum) and a loser-nerd named Schmidt (Jonah Hill) — cross paths again at the police academy, where their friendship bridges the gulf of coolness. Their spectacular incompetence and raw inexperience land them in an undercover operation run out of an abandoned church by an angry captain played by Ice Cube, also heard on the soundtrack expressing a rather critical view of law enforcement in a vintage song by his former group N.W.A.

The juxtaposition of the middle-aged Ice Cube as a foulmouthed cop with the young Ice Cube as a foulmouthed cop hater typifies the movie’s playful, grab-bag idea of itself. There are some obligatory ’80s and early-’90s references, and cameos from some of the old “21 Jump Street” cast members, but aging Generation X nostalgists — not that I have anyone particular in mind — may be disappointed, which is a good thing.

Jenko and Schmidt suffer their own micro-generational displacement, which is much funnier than big shoulder pads, shaggy mullets or acid-washed denim. Sent back to high school, where they masquerade as students, these 20-somethings are shocked to discover how much has changed since 2005. Everybody texts, and the old social hierarchies seem to have broken down. Kids these days are so tolerant and sensitive and environmentally conscious, Jenko notes, with some dismay. “I blame ‘Glee,’ ” he says.

There is, of course, a genetic connection between that show and this movie. On TV “21 Jump Street” was an hourlong youth-targeted Fox prime-time offering that mixed whimsy, emotion and public-service-announcement sobriety as it confronted social ills like bullying, bigotry and drug abuse. The movie takes aggressive satirical aim at exactly this kind of piety without risking true offensiveness. Among the bad guys, for instance, is a clique of diverse, articulate, college-bound, ecology-minded teenagers, led by Eric (Dave Franco), whose very existence destroys the categories Schmidt and Jenko rely on and who are also dealing dangerous drugs.

Eventually action-movie police work overwhelms high-school high jinks, which is too bad, since Mr. Lord and Mr. Miller (who previously directed the chaotic animated children’s film “Cloudy With a Chance of Meatballs”) show no particular distinction in setting up chases and shootouts. The real energy in the film comes from Mr. Hill and Mr. Tatum, who simultaneously fulfill and reverse their buddy-movie stereotypes.

Thanks to the crazy, upside-down world of 2012, and also a clerical mix-up, Schmidt is cast as the big shot — with an only slightly inappropriate romantic possibility played by Brie Larson — while the beefy, bull-necked Jenko is exiled to the world of wonks and dweebs. This may not be a terribly fresh idea, but the two lead actors are nimble and unembarrassable enough to render the identity confusion amusing and even, sometimes, touching.

“21 Jump Street” makes a virtue of its own lack of novelty, reveling in its dumb gags and retrograde attitudes — in 2012 women can actually be funny, guys! — with such unaffected exuberance that you may find yourself not only tickled, but also charmed.

“21 Jump Street” is rated R (Under 17 requires accompanying parent or adult guardian). Far too much raw language for network prime time, but sex, gore and nudity are well within broadcast bounds.

21 Jump Street

DirectorsPhil Lord, Christopher Miller

WriterMichael Bacall

StarsJonah Hill, Channing Tatum, Ice Cube

RatingR

Running Time1h 49m

GenresAction, Comedy, Crime

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Last updated: Mar 30, 2016

A version of this review appears in print on March 16, 2012, on page C15 of the New York edition with the headline: Going Back to High School, Undercover With Badges and Baggage. Order Reprints|Today's Paper|Subscribe